A qualitative analysis of the dynamic characteristics of steerable bo-bos and co-cos

The primary purpose of this study is to provide a qualitative analysis of the differences between the steering characteristics of three axle trucks (commonly referred to as "co-cos"), which are often used in a powered configuration for locomotives, and un-powered two axle trucks (called "bo-bos"), commonly used for railcars. This study extends the results presented by the authors on the curving and hunting benefits of steerable co-cos, using an equivalent stiffness approach. Here, we provide a detailed analytical treatment of the differences that exists between the dynamic characteristics of steerable bo-bos and co-cos. Although there exists a number of anecdotal statements on the ability of steerable trucks in general, and self-steering trucks in particular, there exists no study that provides a thorough qualitative or quantitative analysis of the differences between the steerable co-cos and bo-bos. This study attempts to provide a qualitative analysis of the particular effects of the steering mechanism on lateral stability, curving performance, and traction ability of steerable bo-bos and co-cos. Upon providing a background on self-steering trucks, we describe the bo-bos and co-cos that are widely used by the railroads. Next, we discuss the concept of equivalent stiffness for the two types of trucks. Finally, we discuss the dynamic differences between bo-bos and co-cos, and the design features that must be considered in each truck to optimize their curving, hunting, and adhesion characteristics.